中國與美國考古人員在中國甘肅省嘉峪關(guān)市附近發(fā)現(xiàn)一種獨特恐龍的化石，他們將這種恐龍命名為“雄關(guān)龍”,。雄關(guān)龍化石的發(fā)現(xiàn)可能為了解霸王龍進(jìn)化過程提供新的線索,。
據(jù)悉，雄關(guān)龍化石的年代可追溯到白堊紀(jì)中期,，它可能是“缺失的一環(huán)”,，能夠?qū)⑽覀兪煜さ拇笮桶酝觚埮c其體型較小的祖先聯(lián)系起來,。化石顯示,，雄關(guān)龍帶有一些早期特征,，這些特征后來霸王龍身上變得更為明顯。
古生物學(xué)家對霸王龍家族的了解主要建立在來自白堊紀(jì)時期兩組截然不同的化石基礎(chǔ)之上,，這些化石距今大約1.45億至6500萬年前,。其中一組化石來自白堊紀(jì)早期，也就是巴列姆期,，另一組的年代可追溯到數(shù)千萬年前,。在此之前，古生物學(xué)家一直很難將霸王龍的血統(tǒng)從一組化石追溯到另一組化石,。
美國芝加哥菲爾德博物館副館長,、上演此次雄關(guān)龍化石發(fā)現(xiàn)的中美考古小組負(fù)責(zé)人彼得·馬克維奇(Peter Makovicky)表示：“由于化石記錄數(shù)量極少，我們不得不面對一個4000萬至5000萬年的缺口,。”但他也指出,，雄關(guān)龍化石可能是兩組化石中間“重要的一環(huán)”。馬克維奇說：“我們正在填補化石記錄中缺少的部分,。”此次研究發(fā)現(xiàn)刊登在《皇家學(xué)會學(xué)報B》（Proceedings of the Royal Society B）上,。
馬克維奇及其同事指出，雄關(guān)龍是兩組截然不同的霸王龍之間一個“在系統(tǒng)發(fā)育學(xué),、形態(tài)學(xué)和年代上具有重要意義的環(huán)節(jié)”,。據(jù)悉，此次發(fā)現(xiàn)的雄關(guān)龍已具有大型霸王龍的特征,，例如盒狀頭骨,、支撐大型顎肌的堅固太陽穴骨、改良后鋒利的前牙以及用于支撐頭部的更為強壯的脊骨,。此外，雄關(guān)龍還具備了晚期霸王龍缺失的特征,，例如細(xì)長的鼻子,。一只成年雄關(guān)龍從頭部到臀部的身高可達(dá)到1.5米左右，體重在270公斤上下,。相比之下,，一只成年霸王龍從頭部到臀部的身高則可達(dá)到4米左右，體重更是超過5噸,。
除了馬克維奇等人的研究發(fā)現(xiàn)外,，同一期的《皇家學(xué)會學(xué)報B》還刊登了另外兩篇有關(guān)恐龍化石的論文。其中一篇也是有關(guān)在中國上演的發(fā)現(xiàn),，很多發(fā)現(xiàn)此次雄關(guān)龍的古生物學(xué)家在俞井子盆地發(fā)現(xiàn)了與現(xiàn)代鴕鳥類似的恐龍化石——也就是馬鬃山龍,。雖然此前曾發(fā)現(xiàn)很多似鳥龍化石,，但對這一新恐龍物種的骨骼分析結(jié)果顯示，馬鬃山龍是似鳥恐龍中體型最大的,。據(jù)信,，古生物學(xué)家發(fā)現(xiàn)的馬鬃山龍身高達(dá)到6米，體重在626公斤上下,。
另一篇論文是有關(guān)對在烏茲別克斯坦發(fā)現(xiàn)的鴨嘴龍化石殘骸的分析,，這種鴨嘴龍被命名為“Levnesovia transoxiana”。分析工作是由美國華盛頓史密森尼學(xué)會的漢斯-迪特爾·休斯(Hans-Dieter Sues)以及俄羅斯科學(xué)院的亞歷山大·阿維里安諾夫(Alexander Averianov)完成的,，結(jié)果可能為鴨嘴龍在白堊紀(jì)晚期進(jìn)行的擴(kuò)張?zhí)峁┚€索,。（生物谷Bioon.com）
生物谷推薦原始出處：
Proceedings of the Royal Society B April 22, 2009, doi: 10.1098/rspb.2009.0236
A giant ornithomimosaur from the Early Cretaceous of China
Peter J. Makovicky1,*, Daqing Li2, Ke-Qin Gao3, Matthew Lewin4, Gregory M. Erickson5 and Mark A. Norell6
1Department of Geology, Field Museum of Natural History 1400 South Lake Shore Drive, Chicago, IL 60605, USA
2Fossil Research and Development Center, Gansu Bureau of Geology and Mineral Resources Exploration Lanzhou, Gansu Province 730050, People's Republic of China
3Schools of Earth and Space Sciences, Beijing University Beijing 100871, People's Republic of China
4Department of Ornithology and Mammology, California Academy of Sciences 55 Concourse Drive, San Francisco, CA 94118, USA
5Department of Biological Science, Florida State University King Building, 319 Stadium Drive, Tallahassee, FL 32306-4295, USA
6Division of Paleontology, American Museum of Natural History Central Park West at 79th Street, New York, NY 10024, USA
Abstract
Ornithomimosaurs (ostrich-mimic dinosaurs) are a common element of some Cretaceous dinosaur assemblages of Asia and North America. Here, we describe a new species of ornithomimosaur, Beishanlong grandis, from an associated, partial postcranial skeleton from the Aptian-Albian Xinminpu Group of northern Gansu, China. Beishanlong is similar to another Aptian-Albian ornithomimosaur, Harpymimus, with which it shares a phylogenetic position as more derived than the Barremian Shenzhousaurus and as sister to a Late Cretaceous clade composed of Garudimimus and the Ornithomimidae. Beishanlong is one of the largest definitive ornithomimosaurs yet described, though histological analysis shows that the holotype individual was still growing at its death. Together with the co-eval and sympatric therizinosaur Suzhousaurus and the oviraptorosaur Gigantraptor, Beishanlong provides evidence for the parallel evolution of gigantism in separate lineages of beaked and possibly herbivorous coelurosaurs within a short time span in Central Asia.
Proceedings of the Royal Society B April 22, 2009, doi: 10.1098/rspb.2009.0249
A longirostrine tyrannosauroid from the Early Cretaceous of China
Daqing Li1, Mark A. Norell2, Ke-Qin Gao3, Nathan D. Smith4,5 and Peter J. Makovicky4,*
1Fossil Research and Development Center, Gansu Bureau of Geology and Mineral Resources Exploration Lanzhou, Gansu Province 730050, People's Republic of China
2Division of Paleontology, American Museum of Natural History Central Park West at 79th Street, New York, NY 10024, USA
3School of Earth and Space Sciences, Peking University Beijing 100871, People's Republic of China
4Deptartment of Geology, The Field Museum of Natural History 1400 South Lake Shore Drive, Chicago, IL 60605, USA
5Committee on Evolutionary Biology, University of Chicago 1025 East 57th Street, Chicago, IL 60637, USA
